SPLIT EXHAUST SYSTEM OF A HYBRID VEHICLE WITH EXHAUST-DRIVED ELECTRIC ENGINE AND AIR CONDITIONING COMPRESSOR

Abstract

Vehicle, including: a compressor an exhaust turbine arranged in one path of a split exhaust system of an internal combustion engine; an electric machine mechanically coupled to the compressor and the exhaust turbine; and at least one controller programmed to operate the electric machine according to a difference between a power demand of the compressor and a power output generated by the exhaust turbine; wherein the control is further programmed, in response to the difference being positive, to operate the electric machine as a motor to drive the compressor, and wherein the control is further programmed, in response to the difference being negative, to operate the electric machine as a generator to absorb power from the turbine in order to generate electrical power.

Description

TECHNICAL FIELD

[0001] This application generally relates to the drive of a compressor for an air conditioning system of a hybrid electric vehicle. BACKGROUND

[0002] A hybrid electric vehicle (HEV) includes an internal combustion engine to provide power for propulsion and accessories. The HEV may include one or more electric machines powered by a traction battery to provide power for propulsion and accessories. During operation, the internal combustion engine may drive the electric machines to charge the traction battery. The traction battery may then be discharged to drive the electric machines or other accessories. One accessory is an air conditioning (A / C) compressor to provide cooling in the passenger compartment. The A / C compressor may be driven by an electric machine that draws power from the traction battery. Electrical power for the A / C compressor is supplied from the traction battery or the electric machine driven by the internal combustion engine.The power flow between the combustion engine and the traction battery contains potential for losses. The efficiency of the electric motors, the power electronics, and losses in the traction battery influence the amount of stored energy. For example, US 2012 / 0 273 288 A1, US 2011 / 0 197 582 A1, DE 10 2013 106 643 A1, DE 10 2012 224 427 A1, DE 10 2007 010 027 A1, and DE 10 2006 045 937 A1 disclose the drive of a compressor for an air conditioning system of a hybrid-electric vehicle. SUMMARY

[0003] A vehicle includes at least one controller programmed to operate an electric machine mechanically coupled to a compressor and mechanically coupled to a turbine disposed in a path of a split exhaust system of an internal combustion engine according to a difference between a power demand of the compressor and power generated by the turbine. The controller may be further programmed, in response to the difference being positive, to operate the electric machine as a motor to drive the compressor. The controller may be further programmed, in response to the difference being negative, to operate the electric machine as a generator to absorb power from the turbine to generate electrical power.

[0004] The controller may be further programmed to operate a clutch coupling the electric machine to the compressor based on a requested power demand of the compressor. The controller may be further programmed to disengage the clutch in response to the requested power demand being zero. The controller may be further programmed to disengage a clutch between the turbine and the electric machine in response to the power demand being greater than zero when the internal combustion engine is in a shutdown state. The power demand may be based on a pressure of an air conditioning system.

[0005] A vehicle includes an electric machine coupled to a compressor and an exhaust turbine driven by exhaust gas from an internal combustion engine. The vehicle includes a controller programmed to operate the electric machine to drive the compressor in response to the internal combustion engine being in an auto-stop state, and to operate the electric machine to generate electrical power in response to a power demand from the compressor being zero while the internal combustion engine is running.

[0006] The controller may be further programmed, in response to a power demand of the compressor being greater than a power output from the exhaust turbine, to operate the electric machine to drive the compressor based on a difference between the power demand and the power output. The controller may be further programmed, in response to a power demand of the compressor being less than a power output from the exhaust turbine, to operate the electric machine to generate electrical power based on a difference between the power output and the power demand.

[0007] The vehicle may further include a clutch configured to couple the electric machine to the compressor. The controller may be further programmed to actuate the clutch based on the power demand for the compressor. The controller may be further programmed to engage the clutch in response to the power demand being greater than zero.

[0008] The vehicle may further include a clutch configured to couple the exhaust turbine to the electric machine, wherein the controller is further programmed to engage the clutch in response to the internal combustion engine running. The controller may be further programmed to disengage the clutch in response to the internal combustion engine stopping. The controller may be further programmed to disengage the clutch in response to a state of charge of a traction battery coupled to the electric machine being greater than a predetermined threshold.

[0009] A method includes commanding, by a controller, a torque of an electric machine coupled between an exhaust turbine and a compressor based on a difference between a power demand of the compressor and a power generated by the exhaust turbine. The method further includes operating the electric machine according to the commanded torque.

[0010] The torque can cause the electric machine to operate as a motor to drive the compressor in response to the power demand being greater than the generated power. The torque can cause the electric machine to operate as a generator to convert the difference into electrical energy in response to the power demand being less than the generated power.

[0011] The method may further include operating a clutch between the electric machine and the compressor based on the difference by the controller. The method may further include operating a clutch between the exhaust turbine and the compressor based on the power generated by the exhaust turbine by the controller. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 shows a diagram of a hybrid vehicle illustrating typical powertrain and energy storage components. Fig. Figure 2 shows a diagram of a vehicle including an exhaust turbine configured to drive an electric machine and a compressor. Fig. 3 shows a block diagram representing a control system for controlling the electric machine. DETAILED DESCRIPTION

[0012] Embodiments of the present invention are described herein. It is understood that the disclosed embodiments are merely examples, and other embodiments may take various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, the structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.As will be understood by those of ordinary skill in the art, various features illustrated and described with reference to one of the figures may be combined with features illustrated in one or more other figures to produce embodiments not explicitly illustrated or described. The combinations of illustrated features provide representative embodiments for typical applications. However, various combinations and modifications of the features consistent with the teachings of this disclosure may be desired for particular applications or implementations.

[0013] Fig. 1 shows a typical part-time hybrid electric vehicle (PHEV), although a conventional hybrid electric vehicle (HEV) is equally relevant to the concepts disclosed herein. A typical part-time hybrid electric vehicle 12 may include one or more electric machines 14 mechanically coupled to a hybrid transmission 16. The electric machines 14 may be capable of operating as a motor or a generator. Additionally, the hybrid transmission 16 is mechanically coupled to an internal combustion engine 18. The hybrid transmission 16 is also mechanically coupled to a driveshaft 20, which is mechanically coupled to the wheels 22. The electric machines 14 may provide propulsion and deceleration capability when the internal combustion engine 18 is on or off.The electric machines 14 also function as generators and can provide fuel economy benefits by recovering energy that would normally be lost as heat in a friction braking system. The electric machines 14 can also reduce vehicle emissions by allowing the internal combustion engine 18 to operate at more efficient speeds and, under certain conditions, allow the hybrid-electric vehicle 12 to operate in electric mode with the internal combustion engine 18 off. A powertrain can include those components that generate torque and deliver that torque to a road surface to propel the vehicle. The powertrain can include the internal combustion engine 18, the hybrid transmission 16, the driveshaft 20, and the electric machines 14.

[0014] A traction battery or battery pack 24 stores energy that can be used by the electric machines 14. A vehicle battery pack 24 typically provides a high-voltage direct current output. The traction battery 24 is electrically coupled to one or more power electronics modules. One or more contactors 42 can isolate the traction battery 24 from other components when opened and connect the traction battery 24 to other components when closed. The power electronics module 26 is also electrically coupled to the electric machines 14 and provides the ability to transfer power bidirectionally between the traction battery 24 and the electric machines 14. For example, a typical traction battery 24 may provide a direct current voltage, while the electric machines 14 may be powered by three-phase alternating current to function.The power electronics module 26 can convert the DC voltage into a three-phase AC current to operate the electric machines 14. In a recuperation mode, the power electronics module 26 can convert the three-phase AC current from the electric machines 14, which act as generators, into the DC voltage required by the traction battery 24.

[0015] In addition to providing power for propulsion, the traction battery 24 may provide power to other electrical systems of the vehicle. A vehicle 12 may include a DC / DC converter module 28 that converts the high-voltage DC output of the traction battery 24 to a low-voltage DC power supply compatible with low-voltage loads of the vehicle. An output of the DC / DC converter module 28 may be electrically coupled to an auxiliary battery 30 (e.g., 12V battery). The low-voltage systems may be electrically connected to the auxiliary battery. Other high-voltage loads 46, such as compressors and electric heaters, may be coupled to the high-voltage output of the traction battery 24.

[0016] The vehicle 12 may be a switchable hybrid vehicle in which the traction battery 24 may be charged from an external power source 36. The external power source 36 may be a connection to an electrical outlet. The external power source 36 may be a power distribution network or grid, as provided by an electric utility company. The external power source 36 may be electrically coupled to a charger or electric vehicle supply equipment (EVSE) 38. The EVSE 38 may provide circuitry and controls for regulating and managing the transfer of energy between the power source 36 and the vehicle 12. The external power source 36 may provide DC or AC electrical power to the EVSE 38. The EVSE 38 may include a charging connector 40 for plugging into a charging port 34 of the vehicle 12.The charging port 34 may be any type of port configured to transfer power from the EVSE 38 to the vehicle 12. The charging port 34 may be electrically coupled to a charger or onboard power conversion module 32. The power conversion module 32 may condition the power supplied by the EVSE 38 to provide the proper voltage and current levels to the traction battery 24. The power conversion module 32 may be interconnected with the EVSE 38 to coordinate the delivery of power to the vehicle 12. The EVSE connector 40 may have prongs that mate with corresponding recesses of the charging port 34. Alternatively, various components described as being electrically connected may transfer power using wireless inductive coupling.

[0017] One or more wheel brakes 44 may be provided for decelerating the vehicle 12 and preventing movement of the vehicle 12. The wheel brakes 44 may be hydraulically actuated, electrically actuated, or a combination thereof. The wheel brakes 44 may be part of a braking system 50. The braking system 50 may include other components for operating the wheel brakes 44. For simplicity, the figure shows a single connection between the braking system 50 and one of the wheel brakes 44. A connection between the braking system 50 and the other wheel brakes 44 is implied. The braking system 50 may include a controller for monitoring and coordinating the braking system 50. The braking system 50 may monitor the braking components and control the wheel brakes 44 for vehicle deceleration. The braking system 50 may respond to driver commands and may also operate autonomously to implement features such as stability control.The controller of the braking system 50 may implement a method for applying a requested braking force when requested by another controller or subfunction.

[0018] One or more electrical loads 46 may be coupled to the high-voltage bus. The electrical loads 46 have an associated controller that operates and controls the electrical loads 46 as appropriate. Examples of electrical loads 46 may be a heating module or an air conditioning module.

[0019] Electronic modules in the vehicle 12 may communicate over one or more vehicle networks. The vehicle network may include a plurality of channels for communication. One channel of the vehicle network may be a serial bus such as a control area network (CAN). One of the vehicle network channels may include an Ethernet network, defined by the Institute of Electrical and Electronics Engineers (IEEE) 802 family of standards. Additional channels of the vehicle network may include discrete connections between modules and may include power signals from the auxiliary battery 30. Different signals may be transmitted over different channels of the vehicle network. For example, video signals may be transmitted over a high-speed channel (e.g., Ethernet), while control signals may be transmitted over CAN or discrete signals.The vehicle network can contain any hardware and software components that support the transmission of signals and data between modules. The vehicle network is defined in . Fig. 1, but it may be implied that the vehicle network may connect to any electronic module present in the vehicle 12. A vehicle system controller (VSC) 48 may be present to coordinate the operation of the various components.

[0020] In some configurations, one of the electric loads 46 may be an air conditioning (A / C) compressor driven by an auxiliary electric motor. The auxiliary electric motor may be controlled by an auxiliary power electronics module that converts the traction battery voltage into a current waveform to drive the electric motor. During vehicle operation, the primary power source for the traction battery may be the engine 18. The power flow between the internal combustion engine 18 and the traction battery 24 contains various sources of power loss. A first source of loss may be power loss in the electric drive machine 14 due to inefficiency in converting mechanical energy from rotating the internal combustion engine 18 into electrical energy.A second source of loss may be power loss due to the efficiency of the power electronics module 26 in converting energy between the electric machine 14 and the traction battery 24. A third source of loss may be within the traction battery 24. Internal resistance of the traction battery 24 may cause power loss during charging and discharging of the traction battery 24. Additionally, similar losses are caused by the auxiliary power electronics module and the auxiliary electric motor associated with the A / C compressor. These losses result in reduced fuel economy when an A / C demand is present.

[0021] One way to avoid these conversion losses may be to configure the A / C compressor to be driven directly by the internal combustion engine 18, as a conventional non-hybrid vehicle operates. However, this configuration does not allow operation of the A / C compressor while the internal combustion engine is not running, which can frequently occur in a hybrid-electric vehicle. Such a configuration may cause the internal combustion engine to restart due to a demand for passenger compartment cooling when the vehicle is stopped, resulting in poorer fuel economy.

[0022] Fig. Figure 2 shows a possible improved configuration for driving the A / C compressor 130 with an auxiliary electric machine 122 and an exhaust turbine 118. The A / C compressor 130 can be driven by the auxiliary electric machine 122, which includes a through-shaft that is also driven by the exhaust turbine 118. Such a configuration combines the advantages of both electric and mechanical operation. The improved configuration eliminates the losses caused by the mechanical-to-electrical-to-mechanical conversion process of the electric-only configuration.

[0023] Fig. Figure 2 shows one possible configuration of a system that recovers energy from exhaust flow of the internal combustion engine 18. The internal combustion engine 18 may include a number of combustion chambers or cylinders 104 into which air and fuel are injected. An intake manifold 102 may be coupled to the cylinders 104 via one or more intake ports. Each intake port may supply air and / or fuel from the intake manifold 102 to the cylinders 104. The supply of air and / or fuel may be controlled by intake valves 106 configured to open and close the intake ports. The injected air and fuel are compressed by a piston in the cylinder 104, and a spark is generated to cause combustion and move the piston. The cylinder 104 may have one or more exhaust ports to discharge exhaust gases through an exhaust system.

[0024] The exhaust system may be a split exhaust system in which more than one exhaust path is available to discharge exhaust gases from the internal combustion engine 18. The cylinder 104 may be coupled to one or more exhaust ports configured to discharge combustion gases from the cylinder 104. Exhaust valves 108, 110 associated with the exhaust ports may control the flow of exhaust gas through the exhaust ports by closing and opening the exhaust ports. A first exhaust valve 108 may control a flow of exhaust gas to a first exhaust manifold 112. A second exhaust valve 110 may control a flow of exhaust gas to a second exhaust manifold 114. In some configurations, the flow of exhaust gas may be directed through the first exhaust valve 108 and the second exhaust valve 110 to the same exhaust manifold. The internal combustion engine of Fig. Figure 2 shows two cylinders to demonstrate the general configuration. The illustrated arrangement can be extended to any number of cylinders.

[0025] The operation of the exhaust valves 108, 110 may be coordinated with the combustion cycle of the cylinder 104. The timing for opening and closing the exhaust valves 108, 110 may be controlled by a camshaft. Various techniques for achieving variable valve timing in conjunction with the camshaft may be implemented. The disclosed concepts are not dependent on the particular implementation to achieve variable valve timing, and therefore, there is no intention to limit the implementation to any particular implementation. The purpose of the variable valve timing may be to adjust the timing and flow of exhaust gas through the first exhaust manifold 112 for reasons to be described herein. The variable valve timing may be configured to adjust the amount and timing of exhaust flow through the first exhaust manifold 112 and the second exhaust manifold 114.

[0026] The first exhaust manifold 112 may include an exhaust turbine 118 coupled to the exhaust turbine shaft 136. Exhaust gas flowing past the exhaust turbine 118 may cause the exhaust turbine shaft 136 to rotate. The exhaust turbine shaft 136 may rotate at a speed dependent on a flow rate of the exhaust gas past the exhaust turbine 118. The flow rate of the exhaust gas may be influenced by a pressure differential across the exhaust turbine 118. The pressure differential and flow rate may be influenced by the engine speed and exhaust valve timing. The exhaust turbine shaft 136 may be coupled to a turbine clutch 120. The turbine clutch 120 may also be coupled to an electric machine shaft 124. The turbine clutch 120 may be configured to couple and decouple the exhaust turbine shaft 136 and the electric machine shaft 124.When decoupled, the electric machine shaft 124 can rotate without rotating the exhaust turbine shaft 136. In some configurations, the turbine clutch 120 can be a one-way clutch. In some configurations, the turbine clutch 120 can be a controllable clutch that can be engaged and disengaged via an actuator operable by a controller.

[0027] The vehicle may further include the auxiliary electric machine 122 with an associated rotor and stator. The auxiliary electric machine shaft 124 may be coupled to the rotor of the auxiliary electric machine 122. The auxiliary electric machine shaft 124 may be a through shaft that passes through the auxiliary electric machine 122. The auxiliary electric machine 122 may be electrically coupled to an auxiliary power electronics module 132. The auxiliary power electronics module 132 provides the capability to transfer power bidirectionally between the traction battery 24 and the auxiliary electric machine 122. The auxiliary electric machine 122 may be a permanent magnet AC machine. When the auxiliary electric machine 124 is rotated (e.g., by the exhaust turbine 118), the auxiliary electric machine 122 may be operated to function as a generator.When electrical energy is used to rotate the shaft 124 of the auxiliary electric machine, the auxiliary electric machine 122 functions as a motor. A speed sensor may be coupled to the shaft 124 of the auxiliary electric machine and configured to provide a signal indicative of the shaft speed. The speed sensor may be an encoder, a resolver, or another sensor suitable for measuring speed.

[0028] The flow of exhaust gas through the first exhaust manifold 112 and the second exhaust manifold 114 can affect the performance of the internal combustion engine 18. If the flow of exhaust gas is too restricted, backpressure can affect the operation of a piston in the cylinder 104. The flow of exhaust gas can also affect a subsequent intake stroke if exhaust gas has not been sufficiently purged from the cylinder 104. The first exhaust manifold 112 and the second exhaust manifold 114 can be configured to adjust the flow rate of exhaust gas by balancing these and other considerations. For example, the exhaust turbine 118 can limit the flow rate of exhaust gas through the first exhaust manifold 112. The timing of the opening and closing of the first exhaust valve 108 and the second exhaust valve 110 can be adjusted to minimize pumping losses and thereby optimize fuel economy.

[0029] The auxiliary electric machine 122 may be coupled to an A / C compressor 130. The auxiliary electric machine shaft 124 may be coupled to an A / C compressor shaft 140. The auxiliary electric machine 122 may be coupled to the A / C compressor 130 via a gear set 126 and / or a clutch 128. The auxiliary electric machine shaft 124 may be coupled to the gear set 126, which may be configured to adjust a speed or torque relationship between the auxiliary electric machine shaft 124 and the A / C compressor shaft 140. In some configurations, the gear set 126 may be a planetary gear set. One of the gears of the planetary gear set may be coupled to a compressor clutch 128, which holds the gear stationary when the compressor clutch 128 is engaged. In some configurations, the gear set 126 may include a gear set output shaft 138 coupled to the compressor clutch 128.The compressor clutch 128 can couple the output of the gear set 126 to the A / C compressor shaft 140. Rotation of the A / C compressor shaft 140 drives the A / C compressor 130.

[0030] When operating as a generator, the auxiliary electric machine shaft 124 can be driven by rotation of the exhaust turbine 118. Currents induced in the auxiliary electric machine 122 can be converted by the auxiliary power electronics module 132 to DC voltage levels compatible with the traction battery 24. When operating as a motor, the auxiliary electric machine shaft 124 is driven by electrical energy from the traction battery 24. The auxiliary power electronics module 132 can convert DC voltage from the traction battery 24 into AC currents in the auxiliary electric machine 122.

[0031] The disclosed system allows for distinct operating modes. A first mode may be a direct drive mode of the A / C compressor 130. When the internal combustion engine 18 is running, the exhaust turbine 118 may rotate as exhaust gas flows through the first exhaust manifold 112. In this mode, the A / C compressor 130 may be driven by the exhaust turbine 118. The turbine clutch 120 may be engaged so that the exhaust turbine shaft 136 is coupled to the auxiliary electric machine shaft 124. When the clutch 128 is engaged, the auxiliary electric machine shaft 124 is coupled to the A / C compressor shaft 140. This operating mode allows the A / C compressor 130 to be driven by the exhaust turbine 118 without any intermediate conversion of mechanical energy to electrical energy.

[0032] Furthermore, the power to the A / C compressor 130 can be controlled in this mode by operating the auxiliary electric machine 122. If the exhaust turbine 118 generates more power than is needed to drive the A / C compressor 130, the auxiliary electric machine 122 can operate as a generator. The excess power can be converted into electrical energy to charge the traction battery 24 or to power other high-voltage loads. For example, if the power generated by the exhaust turbine 118 is 5 kW and the A / C compressor 130 consumes 3 kW, 2 kW can be converted into electrical energy.

[0033] This direct mechanical route to driving the A / C compressor 130 is advantageous because it eliminates the intermediate conversion to electrical energy and back. Furthermore, excess energy can be captured from the engine's exhaust stream, which normally goes unused.

[0034] A second operating mode may be an electric drive mode for the A / C compressor 130. In situations where the engine 18 is not running, the auxiliary electric machine 122 may be used to drive the A / C compressor 130. In this operating mode, the exhaust turbine 118 may not rotate because there is no engine exhaust. The auxiliary electric machine shaft 124 may be rotated by operating the auxiliary electric machine 122 as a motor using power from the traction battery 24. The turbine clutch 120 may prevent rotation of the exhaust turbine shaft 136, which would add inertia to the drive by the auxiliary electric machine 122. To operate the A / C compressor 130, the compressor clutch 128 may be engaged to couple the auxiliary electric machine shaft 124 and the A / C compressor shaft 140.In this mode, the A / C compressor 130 may be driven using power from the traction battery 24. The auxiliary electric machine 122 operating mode is advantageous because it allows operation of the A / C compressor 130 while the engine 18 is stopped.

[0035] A third operating mode may be a power generation mode. In situations where the internal combustion engine 18 is running and the A / C compressor 130 is not in use, the exhaust turbine 118 may be used to provide electrical energy. In this mode, the compressor clutch 128 may be disengaged, so that the A / C compressor shaft 140 and the auxiliary electric machine shaft 124 are decoupled. In this mode, the exhaust turbine shaft 136 may rotate and the turbine clutch 120 may be engaged. The auxiliary electric machine shaft 124 may rotate with the exhaust turbine shaft 136, causing the auxiliary electric machine 122 to operate as a generator. The electrical energy may be transferred to the traction battery 24 or used to operate high-voltage loads. The electrical energy generation mode is advantageous because additional electrical energy is generated.Energy from the exhaust stream of the combustion engine that is not normally used is captured.

[0036] One or more controllers 134 may be included to control the operation of the system. The controller 134 may control the operation of the auxiliary power electronics module 132 and the compressor clutch 128. The A / C compressor 130 may be used to build pressure in coolant lines of a thermal system. The thermal system may include a pressure sensor in the coolant lines. The pressure sensor may output a signal indicative of the pressure in the A / C lines. The controller 134 may monitor the pressure signal to determine whether to operate the A / C compressor.

[0037] The controller 134 may determine whether operation of the A / C compressor 130 is requested. Operation of the A / C compressor 130 may be requested based on a setting of the passenger compartment heating / cooling system. In some configurations, the A / C compressor 130 may be requested for active cooling of vehicle components such as the traction battery 24.

[0038] Based on the pressure signal, the speed of the A / C compressor 130 can be controlled to maintain the pressure at a desired level or within a specific range. A control loop can be implemented in the controller 134 to control the speed of the A / C compressor 130 based on a pressure error. The control loop can output a torque or speed request to the auxiliary electric machine 122. In some configurations, the A / C compressor 130 can be operated at a predetermined speed. Based on the request and the pressure signal, the controller 134 can determine an amount of power required to drive the A / C compressor 130.

[0039] The controller 134 may determine an amount of power generated by the exhaust turbine 118. The controller 134 may determine the exhaust turbine power based on a shaft speed. For example, the speed of the auxiliary electric machine shaft 124 may be measured and used to calculate the exhaust turbine speed. The exhaust turbine power may be calculated based on the shaft speed and a speed of the internal combustion engine based on a pre-calibrated lookup table. The pre-calibrated lookup table may be stored in non-volatile memory of the controller 134.

[0040] In power generation mode, the auxiliary electric machine 122 may operate in a speed control loop. A desired speed of the auxiliary electric machine shaft 124 may be maintained. The desired speed may be based on a speed of the internal combustion engine. The desired speed may be based on a predetermined speed of the exhaust turbine shaft 136. The desired speed may be optimized for electricity generation to improve overall efficiency. When operating in the speed control loop, torque limits of the auxiliary electric machine 122 may be set to ensure that the speed of the exhaust turbine 118 is not excessively reduced from a normal operating range. Further, the torque limits may be adjusted based on a state of charge of the traction battery 24.For example, at a predetermined maximum state of charge, the traction battery 24 may be unable to accept further charge. Near the maximum state of charge, the torque limits may be reduced to reduce the amount of energy generated by the auxiliary electric machine 122.

[0041] Controller 134 may determine the exhaust turbine power based on the amount of power absorbed when operating auxiliary electric machine 122 as a generator. Controller 134 may estimate the exhaust turbine power based on engine speed and valve timing. Controller 134 may then adjust a command torque to auxiliary electric machine 122 to reduce the power converted to electricity and increase the amount of power delivered to A / C compressor 130.

[0042] In some configurations, the auxiliary electric machine 122 may be operated in a speed control mode. In the speed control mode, the shaft speed of the auxiliary electric machine 122 may be controlled to a predetermined speed. The predetermined speed may be based on the desired speed of the A / C compressor 130. The predetermined speed may be based on the desired speed of the exhaust turbine 118. The predetermined speed may be dependent on the power demand of the A / C compressor 130 or the desired refrigerant pressure. In the power generation mode, the speed of the auxiliary electric machine 122 may be selected for best efficiency.

[0043] The power of the auxiliary electric machine 122 may be determined based on a difference between the amount of power requested to drive the A / C compressor 130 and the amount of power generated by the turbine 118. A positive difference may indicate that more power is requested to drive the A / C compressor 130. This excess power request may be provided by operating the auxiliary electric machine 122 as a motor. Based on the speed of the auxiliary electric machine shaft 124, a torque level may be calculated for the auxiliary electric machine 122 to supply the power to drive the A / C compressor 130. A negative difference may indicate that some power must be absorbed by the turbine 118. Power may be absorbed by operating the auxiliary electric machine 122 as a generator.Based on the speed of the auxiliary electric machine shaft 124, a torque level for the auxiliary electric machine 122 can be calculated to absorb the difference.

[0044] When operating in a speed control mode, the speed control loop may adjust the torque of the auxiliary electric machine 122. In the event that the power demand of the A / C compressor 130 is greater than the power generated by the turbine 118, the speed of the auxiliary electric machine 122 may fall below the predetermined speed setpoint. The speed control loop may detect the fault and adjust the torque of the auxiliary electric machine 122 to increase the speed (e.g., operate as a motor). In the event that the power demand is less than the generated power, the speed of the auxiliary electric machine 122 may rise above the predetermined speed setpoint. The speed control loop may detect the fault and adjust the torque of the auxiliary electric machine 122 to decrease the speed (e.g., operate as a generator).

[0045] Fig.3 shows a block diagram of a possible control scheme for the system. A difference element 304 may output the difference 306 between the power request 300 of the A / C compressor 130 and the power 302 generated by the exhaust turbine 118. The difference 306 may be input to a control strategy 308. The control strategy may implement a control algorithm based on the difference 306. An electric machine torque request 312 may be output from the control strategy 308 to the electric drive system 314. The electric drive system 314 may represent the operation of the auxiliary power electronics mode 132 and the auxiliary electric machine 122 coupled to the exhaust turbine 118 and the A / C compressor 130. The electric drive system 314 may operate the electric machine in a suitable manner to generate the requested torque 312.The output of the electric drive system 314 may be an electric machine speed 316. The electric machine speed 316 may be an input to the control strategy. The control strategy 308 may further output clutch commands 310 for operating the turbine clutch 120 and the compressor clutch 128. The illustrated system is merely representative of a system for controlling the auxiliary electric machine 122. Other representations are possible. As discussed herein, the power demand 300 and generated power 302 signals may be replaced or supplemented by speed setpoints and a speed control loop.

[0046] The processes, methods, or algorithms disclosed herein may be implementable by / implemented by a processing device, controller, or computer, which may include any existing programmable electronic control unit or dedicated electronic control unit. Likewise, the processes, methods, or algorithms may be stored as data and instructions executable by a controller or computer in many forms, including, but not limited to, information permanently stored in non-writable storage media such as ROM devices and information modifiably stored in writable storage media such as floppy disks, magnetic tapes, CDs, RAM devices, and other magnetic and optical media. The processes, methods, or algorithms may also be implemented in a software executable object.Alternatively, the processes, methods, or algorithms may be embodied in whole or in part using suitable hardware components such as application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), state machines, controllers, or other hardware components or devices, or a combination of hardware, software, and firmware components.

Claims

[1] Vehicle comprising: a compressor, an exhaust turbine arranged in a path of a split exhaust system of an internal combustion engine; an electric machine mechanically coupled to the compressor and the exhaust turbine; and at least one controller programmed to operate the electric machine according to a difference between a power demand of the compressor and a power generated by the exhaust turbine; wherein the controller is further programmed, in response to the difference being positive, to operate the electric machine as a motor to drive the compressor, and wherein the controller is further programmed, in response to the difference being negative, to operate the electric machine as a generator to absorb power from the turbine to generate electrical power. [2] The vehicle of claim 1, wherein the controller is further programmed to operate a clutch coupling the electric machine to the compressor based on a requested power requirement of the compressor. [3] The vehicle of claim 2, wherein the controller is further programmed to disengage the clutch in response to the requested power demand being zero. [4] The vehicle of claim 1, wherein the controller is further programmed to disengage a clutch between the turbine and the electric machine in response to the power demand being greater than zero when the internal combustion engine is in a shutdown state. [5] The vehicle of claim 1, wherein the power request is based on a pressure of an air conditioning system.

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